Refrigerant recovery and purification system

ABSTRACT

A refrigerant recovery system which includes a compressor having an input coupled through an evaporator and through a solenoid valve to the refrigeration system from which refrigerant is to be withdrawn, and an output coupled through a condenser to a refrigerant storage container. The evaporator and condenser are contained within a closed cylindrical canister for heat exchange and oil separation, the canister having an oil drain valve in the bottom. The refrigerant storage container is carried by a scale having a limit switch coupled to control electronics to prevent or terminate further refrigerant recovery when the container is full. The entire system, including the control electronics, is mounted on a two-wheel hand truck to facilitate transport to a job site such as a building air conditioning or heat pump system. Apparatus for purifying recovered refrigerant includes a replaceable core filter/dryer, and a liquid pump for circulating refrigerant from the liquid port of the storage container through the core and then to the container vapor port. A differential pressure gauge is connected across the filter/dryer to indicate need for core replacement. A moisture indicator displays water concentration in the refrigerant. The purification apparatus may be either separate from or combined with the recovery system.

This application is a division of U.S. application Ser. No. 07/528,252filed May 24, 1990, which was a division of U.S. application Ser. No.07/319,618 filed Mar. 3, 1989, now U.S. Pat. No. 4,938,031, which was adivision of U.S. application Ser. No. 07/204,675 filed June 9, 1988, nowU.S. Pat. No. 4,809,520, which was a division of U.S. application Ser.No. 07/117,098 filed Nov. 4, 1987, now U.S. Pat. No. 4,768,347.

The present invention is directed to devices for recovery, purificationand/or storage of used refrigerant from refrigeration systems such asair conditioning and heat pump systems.

BACKGROUND AND OBJECTS OF THE INVENTION

Many scientists contend that release of halogen refrigerants into theatmosphere deleteriously affects the ozone layer which surrounds andprotects the earth from ultraviolet solar radiation. Recentinternational discussions and treaties, coupled with related regulationsand legislation, have renewed interest in devices for recovery andstorage of used refrigerants from refrigeration systems for laterpurification and reuse or for proper disposal. U.S. Pat. No. 4,261,178,assigned to the assignee hereof, discloses a refrigerant recovery systemin which the input of a compressor is coupled through an evaporator andthrough a manual valve to the refrigeration system from whichrefrigerant is to be recovered. The compressor output is connectedthrough a condenser to a refrigerant storage container. The condenserand evaporator are combined in a single assembly through which coolingair is circulated by a fan. Content of the storage container ismonitored by a scale on which the container is mounted for sensingweight of liquid refrigerant in the container, and by a pressure switchcoupled to the fluid conduit between the condenser and the container forsensing vapor pressure within the storage container. A full-containercondition sensed at the scale or a high-pressure condition sensed at thepressure switch terminates operation of the compressor motor. A vacuumswitch is positioned between the inlet valve and the evaporator forsensing evacuation of refrigerant from the refrigeration system andautomatically terminating operation of the compressor motor.

Although the system so disclosed represents a significant advance overprevious refrigerant recovery devices, further improvement remainsdesirable. It is an object of the present invention to provide arefrigerant recovery system of the described character which may bereadily transported to a job site, such as a building air conditioningor heat pump system, which may be operated at such job site to evacuateand store used refrigerant for later purification or disposal, and whichmay be readily physically manipulated and operated by a singlerelatively unskilled operator. Another object of the invention is toprovide a refrigerant recovery system of the described character whichis economical to fabricate and assemble, which is reliable over anextended operating life, and in which the various system components arereadily accessible for repair or replacement as required. In furtheranceof the foregoing objectives, particularly as they relate to portabilityand size reduction, it is another and more specific object of theinvention to provide a combined heat-exchange/oil-separation unit whichwill vaporize incoming refrigerant fed to the compressor input, liquifyrefrigerant fed from the compressor output to the storage container andremove oil from the refrigerant, all without requiring auxiliary aircirculation or cooling as by a separate fan or the like.

Another object of the present invention is to provide apparatus forpurifying recovered refrigerant which is economical, reliable, portableand easy to operate. A further object of the invention is to provide acombined refrigerant recovery and purification apparatus.

SUMMARY OF THE INVENTION

In accordance with one important aspect of the present invention, in arefrigerant recovery system of the character previously described andshown, for example, in the above-noted U.S. Patent, the refrigerantevaporator, condenser and oil separator are combined in a singleintegral assembly within a closed canister having a top wall, a bottomwall and a substantially cylindrical sidewall. The evaporator inlet andoutlet are positioned in the canister for feeding and withdrawingrefrigerant from within the canister adjacent to the canister top wall.Likewise, the condenser inlet and outlet are positioned at the canistertop wall and coupled to a condenser coil which extends within thecanister from the condenser inlet to adjacent the canister bottom wall,and thence to the condenser outlet. An oil drain is positioned in thecanister bottom wall. In the preferred embodiment of the invention, thecondenser coil comprises a pair of coaxially internested coils connectedto each other adjacent to the bottom wall and having substantiallyidentical axial lengths not more than one-half of the axial length ofthe canister. Heat-exchange fins integrally radially outwardly projectfrom the condenser coils. The evaporator inlet includes a baffle andlateral opening for directing incoming refrigerant radially outwardlyagainst the canister sidewall within the canister volume, and theevaporator outlet includes a similar baffle for receiving evaporatedrefrigerant from adjacent a diametrically opposed surface of thecanister sidewall. The canister bottom wall most preferably is dished toenhance oil collection at the oil drain.

In accordance with another important aspect of the present invention,the refrigerant recovery system comprises a self-contained assemblycarried on a wheeled support, most preferably a two-wheel hand truck.The refrigerant container is carried by a scale mounted on the wheeledsupport for indicating a full-container condition. Circuitry forimplementing automatic refrigerant recovery is carried by the wheeledsupport and includes a solenoid valve for selectively admittingrefrigerant to the evaporator, circuitry responsive to an operator forselectively applying electrical power to the solenoid valve and to thecompressor, a pressure sensor at the evaporator inlet, and circuitryresponsive thereto for removing power from the solenoid valve andcompressor upon completion of an evacuation operation. The scale onwhich the recovered refrigerant container is mounted includes a switchfor inhibiting such automated refrigerant recovery operation when thecontainer is full.

In accordance with a further aspect of the invention, apparatus isprovided for purification of refrigerant so recovered. In oneembodiment, the purification apparatus is a stand-alone unit whichcomprises a liquid pump and a filter/dryer mounted in a portable stand.The pump draws recovered refrigerant from the liquid port of the storagecontainer through the filter/dryer, and returns refrigerant to thecontainer vapor port. The filter/dryer has a replaceable core, and adifferential pressure gauge is connected across the filter/dryer forindicating need for core replacement. A moisture indicator is connectedbetween the pump output and the storage container for indicating to anoperator that the refrigerant has been purified. Refrigerant in thecontainer can then be reused for charging air conditioning systemsusing, for example, charging apparatus of the character disclosed inU.S. Pat. No. 4,688,388 assigned to the assignee hereof. In a secondembodiment, the purification apparatus and recovery system are combinedin a single stand-alone portable unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objects, features and advantagesthereof, will be best understood from the following description, theappended claims and the accompanying drawings in which:

FIG. 1 is a front elevational view of a self-contained portablerefrigerant recovery and storage system in accordance with a presentlypreferred embodiment of the invention;

FIG. 2 is a rear elevational view of the system of FIG. 1;

FIG. 3 is a schematic diagram of the refrigerant recovery system ofFIGS. 1 and 2;

FIG. 4 is a partially sectioned elevational view of theheat-exchange/oil-separation unit utilized in the system of FIGS. 1-3;

FIG. 5 is an electrical schematic diagram of the control electronics inthe system of FIGS. 1-2;

FIG. 6 is a schematic diagram similar to that of FIG. 3 but illustratinga modified embodiment of the invention;

FIG. 7 is a front elevational view of a refrigerant purification systemin accordance with another embodiment of the invention;

FIG. 8 is a side elevational view of the system of FIG. 7;

FIG. 9 is a schematic diagram of the purification system of FIGS. 7 and8 in operation;

FIG. 10 is a front elevational view of a combined recovery andpurification system in accordance with a further embodiment of theinvention;

FIG. 11 is a plan view of the control panel in the system of FIG. 10;and

FIG. 12 is a schematic diagram of the system of FIGS. 10-11.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1-3 illustrate a presently preferred embodiment of a refrigerantrecovery and storage system 10 in accordance with the present inventionas comprising a hand truck 12 which includes a vertical frame 14supported by a pair of wheels 16. A compressor 18 is carried by theshock-mounts 20 on a forwardly extending base 22 of frame 14. Compressor18 has an inlet which is coupled by the conduit 24, 25 through theevaporator section of a combined heat-exchange/oil-separation unit 26mounted on the vertically-extending panel 29 of frame 14 abovecompressor 18, and through a conduit 25 and an electrically operatedsolenoid valve 28 to an input manifold 30. Manifold 30 is mounted onpanel 29 adjacent to unit 26, and includes a pair of hoses 32, 33 forconnection to the high pressure and low pressure sides of arefrigeration system from which refrigerant is to be recovered. Manifold30 also has the usual manual valves 34, 35 and pressure gauges 36, 37. Apressure switch 40 (FIG. 3) is connected between solenoid valve 28 andthe evaporator portion of heat-exchange/oil-separation unit 26, and isresponsive to a predetermined low pressure to the compressor input fromthe refrigeration system to indicate removal of refrigerant therefrom.

The outlet of compressor 18 is connected by the conduits 42 through thecondenser portion of heat-exchange/oil-separation unit 26, through acheck valve 44 and through a pair of manual valves 46, 48, in series, tothe vapor inlet port 49 (FIG. 3) of a refillable refrigerant storagecontainer 50. Container 50 is of conventional construction and includesa second port 52 for coupling to a suitable fill level indicator 53, apressure relief port 54, and a manual liquid valve 56 connected to aliquid port 57. A suitable container 50 is marketed by Manchester TankCompany under the trademark "ULTRALINE" and includes valves 48, 56, apressure relief valve at port 54 and a fill indicator 53 coupled to port52 as part of the overall assembly. A pressure switch 58 is connected inline between check valve 44 and manual valve 46, and is responsive tovapor pressure within container 50 with valves 46, 48 open to indicatean excessive vapor pressure of predetermined level therewithin.

Storage container 50 is carried on a platform 60 which is pivotallymounted by the hinge pin 62 to the back side of truck frame 14. A flathorizontal base 64 projects rearwardly from frame 14 beneath platform60, and a pair of coil springs 66 are captured in compression betweenplatform 60 and base 64 at an edge of platform 60 spaced from frame 14.A limit switch 68 is mounted on base 64 and has a switch-actuating arm70 which projects upwardly therefrom for engagement with theframe-remote edge of platform 60. Platform 60, hinge 62, frame 14, base64, springs 66 and limit switch 68 thus form a scale 72 in which limitswitch 68 is effectively responsive to a predetermined weight ofrefrigerant within container 50 to indicate a full container conditionto the control electronics 74 (FIGS. 1 and 5). Weight sensed by limitswitch 68 is adjustable through selection of or bias on spring 66 and/orpositioning of switch actuator 70. A strap or belt 75 (FIG. 2) holdscontainer 50 on truck 12 when the latter is tilted rearwardly by handles76 for transport.

FIG. 4 illustrates heat-exchange/oil-separation unit 26 in greaterdetail as comprising a canister 80 having a closed or imperforategenerally cylindrical sidewall 82 and an outwardly dished bottom 84having a manual oil drain valve 86 centrally positioned therein. Theevaporator portion of unit 26 includes an inlet fitting 88 and an outletfitting 90 carried by the outwardly concaved top 92 of canister 80.Inlet fitting 88 comprises the threaded nipple 94 coupled to the hollowpipe 96 which has an opening 98 facing laterally outwardly towardcanister sidewall 82 immediately beneath top 92. A slanted or slopeddeflector or baffle 100 forces incoming refrigerant laterally outwardlybeneath the canister top into the open internal volume of canister 80.Similarly, outlet fitting 90 has a threaded nipple 94 and a pipe 96,with the side opening 98 and baffle 100 oriented laterally diametricallyoppositely of the identical opening in inlet fitting 88 for receivingand feeding refrigerant from the open volume of canister 80 to the inletof compressor 18.

The condenser portion of unit 26 includes an inlet fitting 102 and anoutlet fitting 104 interconnected within canister 80 by a continuouslength of tubing or conduit which forms a closed condenser coil 106.More specifically, coil 106 includes an inner coil 108 coupled at itsupper end to inlet fitting 102, and an outer coil 110 coupled at itsupper end to outlet fitting 104 Coils 108, 110 are tightly formedspirals or helices coaxially internested and integrally connected toeach other at their lower ends adjacent to canister bottom 84. Coil 106is thus suspended from canister top 92 by the lengths of coil conduitcoupled to fittings 102, 104 while being spaced from the canister sideand bottom walls, with the convolutions of each coil 108, 110 occupyingless than one-half of the overall axial dimension of canister 80. Theconduit which forms condenser coil 106 is preferably of copper or othersuitable construction and has heat exchange fins integrally radiallyoutwardly projecting therefrom. Each fitting 102, 104 includes athreaded nipple 114.

In operation of heat-exchange/oil-separation unit 26, incoming liquid ormixed liquid and vapor refrigerant from the refrigeration system beingevacuated is fed through fitting 88, with the liquid refrigerant fallingby gravity onto and around coil 106. At the same time, vapor from thecompressor outlet is fed through condenser inlet 102 to coil 106, whereheat is lost from the compressed refrigerant vapor and transferred tothe liquid refrigerant which externally surrounds coil 106. Such heatedliquid refrigerant is evaporated and drawn through evaporator outlet 90to the compressor input. In the meantime, the compressor output isliquified by heat loss in condenser coil 106 and fed through condenseroutlet 104 to storage container 50 (FIGS. 1-3). Oil entrained inincoming liquid refrigerant is not revaporized in the evaporator portionof unit 26, but pools in liquid phase at dished bottom 84 of unit 26 andmay be removed as desired through valve 86.

FIG. 5 is a schematic diagram of control electronics 74 carried behindan operator panel 116 (FIG. 1) mounted to truck frame 14 above unit 26.Recovery pressure switch 40, scale switch 68 and tank pressure switch 58are connected in series with an operator power switch 121 (FIGS. 1 and5), an operator start-cycle pushbutton 122 and the coil of a controlrelay 1CR across a 120 VAC source of electrical power. A first set ofnormally-open contacts 1CR-1 of control relay 1CR is connected acrossoperator start-cycle pushbutton 122. A second set of normally-opencontacts 1CR-2 is connected in series with power switch 121 andcompressor 18 across 120 VAC. The solenoid 2CR of valve 28 is connectedacross compressor 18, as is the compressor-on lamp 124 (FIGS. 1 and 5).A full-tank lamp 126 is connected across scale switch 68, and ahigh-pressure lamp 128 is connected across pressure switch 58. Aresistor 130 is connected across switch 40, the coil of relay 1CR andpush button 122 to provide a current path for lamps 126, 128.

In operation of the overall system 10, hoses 32 are first connected tothe refrigeration system to be evacuated in the usual manner, and one orboth valves 34, 35 are opened. Scale switch 68 is normally closed, andassumes an open condition when actuator arm 70 is engaged by platform60. Pressure switch 58 is normally closed, and assumes an open conditionwhen the vapor pressure within container 50 exceeds the switch thresholdlevel. Recovery pressure switch 40 is likewise normally closed, andassumes an open condition when the pressure to the compressor input fromthe refrigeration system decreases below the switch pressure level. Withpower switch 121 closed to apply power to the system, the operatordepresses pushbutton 122 to begin a recovery cycle, whereupon the coilof control relay 1CR is energized through closed switches 40, 58, 68,121 and 122. Contact set 1CR-1 closes to maintain a current path throughthe coil of relay 1CR when pushbutton 122 is released. Likewise, contactset 1CR-2 closes to apply power to compressor 18 and solenoid valve 28to open the solenoid valve and energize the compressor. Liquidrefrigerant is then withdrawn from the refrigeration system through theevaporator stage of unit 26, compressed by compressor 18, reliquified atthe condenser stage of unit 26, and fed to storage container 50. Whensubstantially all of the refrigerant has been withdrawn from therefrigeration system, recovery pressure switch 40 opens, relay 1CR isde-energized, and power is removed from compressor 18 and solenoid valve28. In the event that platform 60 engages scale switch 68 to indicate afull condition at storage container 50, switch 68 opens and lamp 26 isilluminated, either through switch 58 and resistor 130 or through lamp128 and resistor 130. Likewise, if high tank vapor pressure opens switch58, lamp 128 is illuminated through resistor 130 and either lamp 126 orswitch 68. In either event, the open condition of switch 58 and/or 68prevents energization of relay 1CR independently of operator pushbutton122. Opening of either switch 58 or 68 during a recovery cycle willde-energize relay 1CR and thereby terminate the cycle.

FIG. 6 illustrates a simplified refrigerant recovery system 140 inaccordance with a modified embodiment of the invention for use with aseparately-provided storage container (not shown). System 140 includessolenoid valve 28 which is directly coupled to the refrigeration system,recovery pressure switch 40, heat-exchange/oil-separation unit 26,compressor 18, check valve 44 and manual valve 46 for feeding liquidrefrigerant to such separately-provided storage container. Controlelectronics for system 140 of FIG. 6 is similar to that illustrated inFIG. 5, but with switches 68, 58, lamps 126, 128 and resistor 130eliminated. The advantage of system 140 is that the same is of suchcompact structure as to be contained within a portable suitcase-likeenclosure which may be readily transported by the operator to the jobsite along with a separate storage container.

FIGS. 7-9 illustrate a stand-alone device 140 for purification ofrecovered refrigerant within storage container 50. A liquid pump 142 ismounted on the base 144 of an L-shaped stand 146. A replaceable corefilter/dryer unit 148 of any suitable conventional type is mounted onthe back 150 of stand 146 above pump 142. Stand 146 rests on the rubbermounts 152. A hose 154 extends from the inlet of unit 148 through amanual valve 156 to a coupling 158 for connection to the liquid port 57of container 50 at valve 56. The outlet of unit 148 is connected by thehose 160 to the inlet of pump 142, and the outlet of pump 142 isconnected by the hoses 162 through a moisture indicator 164 and a manualvalve 166 to a coupling 168 for connection to the vapor port 49 ofcontainer 50 at valve 48. A differential pressure gauge 170 is connectedacross filter/dryer unit 148. Electrical power is selectively applied topump 142 through a power cord 172 and an operator power switch 174. Anelongated opening 176 at the upper edge of back 150 permits manualgrasping and transportation of the entire device 140. i.e., Gauge 170and switch 174 are mounted within a housing 178 fastened to back 150 ofstand 146 adjacent to unit 148.

In operation, the operator first attaches couplings 158, 168 tocontainer 50, and then opens valves 48, 56, 156, 166. Power is thenapplied to pump 142 through switch 174, and liquid is drawn from thelower portion of container 50, circulated through filter/dryer unit 148and pump 142, and returned to the upper portion of container 50 at vaporport 49. This process continues until moisture indicator 164 indicatesremoval of all moisture from the refrigerant, at which time operation isterminated and container 50 disconnected. The refrigerant withincontainer 50 is then ready for reuse to recharge refrigeration systems.Suitable recharge apparatus is disclosed in U.S. Pat. No. 4,688,388assigned to the assignee hereof. When differential pressure gauge 170indicates a pressure drop across unit 148 above a preselected threshold,which may be marked on the indicator, the operator replaces thefilter/dryer core of unit 148.

FIGS. 10-12 illustrate a combined recovery/purification system 180 inaccordance with yet another embodiment of the invention. System 180includes many components of system 10 (FIGS. 1-5) and 140 (FIGS. 7-9)hereinabove described in detail, with identical reference numeralsindicating correspondingly identical elements. In system 180, a singleinput coupling 182 (FIG. 12) replaces manifold 30 (FIGS. 1 and 3). Pump142 is mounted on base 22 adjacent to compressor 18, and filter/dryerunit 148 is mounted on frame back panel 29 above pump 142. The outlet ofpump 142 is fed through moisture indicator 164 and through a check valve184 (FIG. 12) to a T-coupler 186 connected between check valve 44 andvalve 156. A pressure relief valve 188 is connected between the outletof filter/dryer unit 148 and the inlet of pump 142.Heat-exchange/oil-separation unit 26, valves 28, 44, 184 and 188, andpressure switches 40, 58 are contained within an enclosure 190 mountedon frame 14. The operator controls and indicators --i.e., switches 121,122, 174, lamps 124, 176, 128, gauge 170, moisture indicator 164 and apurification pump power lamp 192 --are mounted on a sloping controlpanel 194 of enclosure 190 and are suitably labeled as shown in FIG. 11for ease of use.

It will be appreciated that the refrigerant recovery and purificationsections of the combined system of FIGS. 10-12 can be operatedindividually as hereinabove described in detail. It is intended that therefrigerant recovery section of the combined unit be employed untilcontainer 50 is full. The purification section may then be operateduntil the recovered refrigerant is purified, at which time container 50may be replaced with an empty container. Purification of a fullcontainer should take about one hour. Tank-full switch 68 and pressureswitch 58 do not inhibit operation of the purification apparatus.Furthermore, the recovery and purification sections of the combined unitmay be operated simultaneously, although such operation would lengthenrecovery time.

The invention claimed is:
 1. Apparatus for purification of refrigerantwithin a storage container having separate liquid and vapor ports, saidapparatus comprising filter/dryer means for removing water fromrefrigerant passing therethrough, a liquid refrigerant pump, means forremovably connecting said filter/dryer means and said pump to said portsto circulate liquid refrigerant in a closed path from said liquid portthrough said filter/dryer means and said pump to said vapor port, meansfor indicating water concentration in refrigerant in said path, andmeans coupled to said filter/dryer means for indicating operativecondition of said filter/dryer means.
 2. The system set forth in claim 1wherein said condition-indicating means comprises differential pressuremeans connected across said filter/dryer means.
 3. The system set forthin claim 4 wherein said apparatus is mounted on an L-shaped stand havinga base and a back, said back including handle means at an upper edgethereof for manually transporting said apparatus.
 4. Apparatus forpurification of refrigerant within a storage container having separateliquid and vapor ports, said apparatus comprising filter/dryer means forremoving water from refrigerant passing therethrough, a liquidrefrigerant pump, means for removably connecting said filter/dryer meansand said pump to said ports to circulate liquid refrigerant in a closedpath from said liquid port through said filter/dryer means and said pumpto said vapor port, and means in said path for indicating operativecondition of said filter/dryer means.
 5. The system set forth in claim30 wherein said condition-indicating means comprises means forindicating water concentration in refrigerant in said path.